Flexible display panels have gradually become the mainstream of the display field because of their following advantages: light and thin, bendable, capable of being amounted on an irregular surface, and capable of being made to a wearable device etc. The flexible display panel can achieve foldable display by a liquid crystal display (LCD) or an organic light-emitting diode (OLED). In the display technology for realizing flexible display, the OLED has become a research hotspot in the flexible display field in recent years, because it has excellent performances, such as self-luminescent, fast response, wide viewing angle, high brightness, low power consumption, and easier to be bent with a smaller bending radius etc. Meanwhile, with the development of technologies such as touch control technology and fingerprint recognition technology etc., function modules have been widely applied to various electronic products and are gradually extended to wearable devices. Currently, the flexible display device which integrates the function module with the flexible display panel has attracted widespread attentions.